Coating composition

ABSTRACT

A coating composition including an ionic polymer (a), a hygroscopic agent (b) and a solvent, the hygroscopic agent (b) being a granular crosslinked product of a monovalent metal salt of a poly(meth)acrylic acid and being contained in an amount of 75 to 700 parts by mass per 100 parts by mass of the ionic polymer (a).

TECHNICAL FIELD

This invention relates to a coating composition capable of forming ahygroscopic coating on the surfaces of various kinds of base materials.More specifically, the invention also relates to a coating formed byusing the coating composition.

BACKGROUND ART

Leakage of electric charge must be avoided in a variety of kinds ofelectronic devices that have been developed and put into practical usein recent years, such as organic electroluminescent (organic EL)devices, solar cells, touch panels, electronic papers, etc. Therefore, ahigh degree of water barrier property is required for the plastic basematerials that are used for forming circuit boards and for the plasticbase materials such as films that are used for sealing the circuitboards.

The water barrier property can be realized by providing a hygroscopiccoating in which a hygroscopic agent is dispersed.

For instance, a patent document 1 is disclosing a gas barrier laminateobtained by forming an inorganic barrier layer on the surface of aplastic base material, and forming, on the inorganic barrier layer, asealing layer (hygroscopic film) in which nano particles such as of ametal oxide or carbon nano tubes are dispersed as a hygroscopic agent.

Further, a patent document 2 proposes a gas barrier laminate (film)obtained by forming an inorganic barrier layer, an organic layer and awater-trapping layer (hygroscopic film) on a base film. Here, ahygroscopic material such as silica gel or aluminum oxide is dispersedin water-trapping layer (hygroscopic film) and in a high molecularbinder such as polyamide.

Further, a patent document 3 discloses a gas barrier laminate comprisinga plastic base material on which are deposited a gas barrier film and ahygroscopic layer (hygroscopic film), the hygroscopic layer containingan alkylene oxide, nano particles of acrylate or an organic metalcomplex.

While studying many such hygroscopic films, the present inventors havediscovered that if a matrix of an ionic polymer contains dispersedtherein a hygroscopic agent having such a hygroscopic property that thehumidity thereof that is attained is lower than the humidity of thematrix, then a very high water barrier property is exhibited, and havepreviously filed a patent application (PCT/JP2014/052788). Then theinventors have furthered the study and have discovered that if acrosslinked product of a monovalent metal salt of an acrylic acid isused and if the hygroscopic agent is added in a predetermined range,then the hygroscopic film exhibits a high hygroscopic property (watershut-off property) as well as excellent transparency and surfacesmoothness.

PRIOR ART DOCUMENTS Patent Documents

Patent document 1: JP-A-2010-511267Patent document 2: JP-A-2009-90633Patent document 3: JP-A-2011-131395

OUTLINE OF THE INVENTION Problems that the Invention is to Solve

It is, therefore, an object of the present invention to provide acoating composition capable of forming a coating that exhibits excellenthygroscopic property, transparency and surface smoothness.

Another object of the present invention is to provide a coating formedby using the above coating composition.

A further object of the present invention is to provide a coating thatcan be favorably used as a defogging film or a water shut-off film.

Means for Solving the Problems

According to the present invention, there is provided a coatingcomposition comprising an ionic polymer (a), a hygroscopic agent (b) anda solvent, the hygroscopic agent (b) being a granular crosslinkedproduct of a monovalent metal salt of a poly(meth)acrylic acid and beingcontained in an amount of 75 to 700 parts by mass per 100 parts by massof the ionic polymer (a).

The coating composition of the present invention is used, particularlypreferably, for forming a defogging film or a water shut-off film. Asthe ionic polymer (a), there can be used a cationic polymer (a1) or ananionic polymer (a2).

According to the present invention, further, there is provided a coatingformed on the surface of a base material, the coating comprising amatrix of an ionic polymer (a) and a hygroscopic agent (b) dispersed inthe matrix, and the hygroscopic agent (b) being a granular crosslinkedproduct of a monovalent metal salt of a poly(meth)acrylic acid and beingcontained in an amount of 75 to 700 parts by mass per 100 parts by massof the ionic polymer (a).

The coating is formed by applying the above-mentioned coatingcomposition on the surface of a base material followed by heating toremove the solvent. The coating has a haze of 5% or less and a maximumsurface roughness Ra (JIS B-0601-1994) of 0.1 μm or less.

The coating is favorably used as a water shut-off film or a defoggingfilm.

Effects of the Invention

Upon being applied onto the surface of a predetermined base material andheated, the coating composition of the invention forms a coating of astructure in which the matrix is formed by the ionic polymer (a) andhygroscopic agent (b) is dispersed in the matrix. As proved by theresults of experiments in Examples appearing later, the coating exhibitsa very high hygroscopic property and undergoes a change in volume(swells) in a very suppressed manner despite it has absorbed humidity.

The coating, further, features a high degree of transparency and surfacesmoothness.

For example, as demonstrated in Examples appearing later, the coatingformed by using the coating composition of the present invention has ahaze of 5% or less, a very high degree of transparency, a maximumsurface roughness Ra (JIS B-0601-1994) of 0.1 μm or less and a highdegree of surface smoothness.

The coating having the above-mentioned properties is favorably used, forexample, as a defogging film. Namely, upon coating the surfaces ofmirrors, windowpanes and transparent containers with the coatingcomposition, the water droplets that happen to adhere on the surfaces ofthe coatings turn into a thin and smooth water film. This, therefore,effectively alleviates irregular reflection or scattering of lightcaused by water droplets; i.e., fogging due to the adhesion of waterdroplets is alleviated. That is, the coating serves as a defogging filmand effectively suppresses a decrease in the optical properties causedby the fogging on the base materials.

Further, on a transparent substrate (e.g., glass substrate) holding aluminous layer of an organic electroluminescent device (organic ELdevice), the coating formed thereon works as a water shut-off film byabsorbing very small amounts of water in the device, and effectivelyalleviates the deterioration of the luminous layer caused by themoisture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating hygroscopic property of a coating formedby using a coating composition of the present invention.

FIG. 2 is a graph showing degrees of humidity attained by a cationicpolymer, a hygroscopic agent and a mixture of the cationic polymer andthe hygroscopic agent at a ratio of 1:1 at different temperatures.

MODES FOR CARRYING OUT THE INVENTION

The coating composition of the present invention contains the ionicpolymer (a), hygroscopic agent (b), solvent and, as required, otheradditives. By applying the coating composition onto the surface of apredetermined base material and by heating the coating composition toremove the solvent, there is formed a coating thereof. The coating has astructure in which the ionic polymer (a) forms a matrix in which thereis dispersed the hygroscopic agent (b) which is a granular crosslinkedproduct of a monovalent metal salt of a poly(meth)acrylic acid. Due tothis dispersion structure, the coating exhibits excellent hygroscopicproperty which is a basic property thereof.

<Principle of Hygroscopic Property>

Hygroscopic property of the coating formed by using the coatingcomposition of the invention will be described with reference to FIG. 1.

In the coating formed on a predetermined base material shown in FIG. 1,the matrix is formed by an ionic polymer or, concretely, by a cationicpolymer (ionic groups are NH₂ group) or by an anionic polymer (ionicgroups are COONa groups and COOH groups). In the polymer, there isdispersed, as a hygroscopic agent, the granular crosslinked product of amonovalent metal salt of a poly(meth)acrylic acid (see FIG. 1(A)).

That is, with the above-mentioned coating formed on the predeterminedbase material, a very small amount of water that has permeated throughthe base material or water in the atmosphere is absorbed by the matrixthat contains hydrophilic cationic groups or anionic groups (see FIG.1(B)). Namely, the matrix by itself exhibits a high hygroscopicproperty.

Here, if the matrix simply absorbs water, then water that is absorbedwill be easily released due to a change in environment such as a rise intemperature. Besides, water that has infiltrated widens the gaps amongthe polymer molecules that are forming the matrix. As a result, thecoating swells and loses dimensional stability.

In the present invention, on the other hand, the granular crosslinkedproduct of the monovalent metal salt of the poly(meth)acrylic aciddispersed as the hygroscopic agent in the matrix has a hygroscopicproperty larger (attains at a humidity lower) than that of the cationicpolymer or the anionic polymer that is forming the matrix. Therefore,water absorbed in the matrix is, further, trapped by the hygroscopicagent (see FIG. 1(C)). This effectively suppresses the coating fromswelling despite it has absorbed the water molecules. Besides, the watermolecules are confined in the coating (matrix); i.e., release of waterfrom the coating is effectively prevented. As described above, thecoating formed by using the coating composition of the present inventionhas double functions of trapping water and confining water therein owingto its high hygroscopic capability. The coating, therefore, exhibitsexcellent hygroscopic property and anti-swelling property (dimensionalstability).

For instance, in Examples appearing later, the below-mentionedexperiments have been carried out in order to prove that water trappedby the matrix is, further, confined in the hygroscopic agent.

That is, 0.5 g of a material to be measured was dried at 140° C. for onehour. Thereafter, the material was put together with a wirelessthermometer/hygrometer (Hygroclone manufactured by KN Laboratories,Inc.) into a water-impermeable steel foil-laminated cup of a volume of85 cm³ in an atmosphere of 30° C. 80% RH. The container was sealed atits mouth portion with a lid of an aluminum foil-laminated film, and wasleft to stand for one day. The container was, thereafter, left to standat temperatures of −20, 5, 22, 30 and 40° C. for 3 hours each, and therelative humidities in the cup were regarded to be the attainedhumidities at each of these temperatures.

FIG. 2 shows humidities attained by the cationic polymer(polyallylamine), by the hygroscopic agent (TAFTIC HU820E) and by amixture of the cationic polymer and the hygroscopic agent at a ratio of1:1 at different temperatures. With the cationic polymer, the humidityin the container increased accompanying an increase in the temperature.With the hygroscopic agent and the mixture of the cationic polymer andthe hygroscopic agent, on the other hand, the humidity in the containercould be lowered to near the absolute dry state. The mixture exhibitedthe hygroscopic capability equivalent to the simple hygroscopic agenttelling the fact that water absorbed by the cationic polymer was notreleased to the exterior despite of a rise in the temperature butremained trapped by the hygroscopic agent that has a larger hygroscopicproperty (i.e., attains a lower humidity).

As will be understood from FIG. 1, further, with the crosslinkedstructure being introduced in the matrix, gaps among the molecules ofthe ionic polymer is suppressed from expanding despite water hasinfiltrated. Therefore, the coating is more effectively suppressed fromswelling despite it has absorbed water.

<Ionic Polymer (a)>

In the invention, the ionic polymer (a) is a component that forms thematrix of the coating. As also shown in FIG. 1, the ionic polymer (a)can be either a cationic polymer (a1) or an anionic polymer (a2).

Cationic Polymer (a1);

In the invention, the cationic polymer (a1) used as the matrix componentin the coating is a polymer having a cationic group that could become apositive electric charge in water, such as primary to tertiary aminogroup, quaternary ammonium group, pyridyl group, imidazole group orquaternary pyridinium group in the molecules thereof. The cationicpolymer of this kind is capable of forming a hygroscopic matrix sincethe cationic group therein has a strong nucleophilic action and trapswater by the hydrogen bond.

The amount of the cationic groups in the cationic polymer (a1) may,usually, be such that the water-absorbing ratio (JIS K-7209-1984) of thehygroscopic matrix that is formed is 20% or more and, specifically, 30%to 45% in an atmosphere of a humidity of 80% RH and 30° C.

As the cationic polymer (a1), further, there can be used at least onekind of cationic monomer as represented by an amine type monomer, suchas allylamine, ethyleneimine, vinylbenzyltrimethylamine,[4-(4-vinylphenyl)-methyl]-trimethylamine or vinylbenzyltriethylamine; anitrogen-containing heterocyclic monomer such as vinylpyridine orvinylimidazole; or salts thereof, suitably being polymerized orcopolymerized with other monomers copolymerizable therewith and,further, as required, partly neutralized by the treatment with an acid.

As the other monomers copolymerizable therewith, though not limitedthereto only, there can be exemplified styrene, vinyltoluene,vinylxylene, α-methylstyrene, vinylnaphthalene, α-halogenated styrenes,acrylonitrile, acrolein, methyl vinyl ketone and vinylbiphenyl.

Instead of using the above cationic monomer, further, it is alsoallowable to use a monomer having a functional group capable ofintroducing the cationic functional group, such as styrene,bromobutylstyrene, vinyltoluene, chloromethylstyrene, vinylpyridine,vinylimidazole, α-methylstyrene or vinyl naphthalene. After thepolymerization, the treatment is executed such as amination oralkylation (conversion into a quaternary ammonium salt) to obtain thecationic polymer (a1).

In the invention, among the above cationic polymers (a1), it is desiredto use, specifically, the polyallylamine from the standpoint of formingthe film.

In the invention which uses the above cationic polymer (a1) as thematrix component, a certain kind of crosslinking agent is used tointroduce a crosslinked structure in the matrix, however, without usingany particular adhesive offering an advantage of improved adhesivenessto various kinds of base materials coated with the coating composition.

The polymerization for forming the cationic polymer (a1) is, usually,carried out based on the radical polymerization by heating while using apolymerization initiator.

As the polymerization initiator, though not specifically limited, therecan be representatively used organic peroxides such as octanoylperoxide, lauroyl peroxide, t-butylperoxy-2-ethyl hexanoate, benzoylperoxide, t-butylperoxyisobutylate, t-butylperoxy laurate, t-hexylperoxybenzoate, and di-t-butyl peroxide. Usually, the polymerization initiatoris used in an amount of about 0.1 to about 20 parts by mass and,specifically, about 0.5 and about 10 parts by mass per 100 parts by massof the cationic monomer (or a monomer capable of introducing thecationic groups).

The cationic polymer (a1) is obtained by conducting the polymerizationas described above. If there is used a monomer capable of introducingthe cationic functional group, however, a treatment may be conducted forintroducing cationic groups, such as amination or alkylation treatmentafter the polymerization has been finished.

Anionic Polymer (a2);

In the invention as shown in FIG. 1, it is also allowable to use theanionic polymer (a2) as the ionic polymer (a) for forming the matrix inthe coating.

The anionic polymer (a2) is a polymer which has in the molecules thereofan anionic functional group that could become a negative electric chargein water, such as carboxylic acid group, sulfonic acid group orphosphonic acid group, or an acid base thereof that is partlyneutralized. The anionic polymer is capable of forming a hygroscopicmatrix since the functional group therein traps water due to thehydrogen bond.

The amount of the anionic functional groups in the anionic polymer (a2)may differ depending on the kind of the functional groups but is,usually, in such an amount that the water-absorbing ratio (JISK-7209-1984) of the hygroscopic matrix that is formed is not 20% or moreand is, specifically, 30% to 45% in an atmosphere of a humidity of 80%RH and 30° C.

The anionic polymer (a2) having the above functional group is obtainedby polymerizing or copolymerizing, with other monomers copolymerizabletherewith, at least one of the anionic monomers as represented bycarboxylic acid monomers such as methacrylic acid, acrylic acid andmaleic anhydride; sulfonic acid monomers such as α-halogenatedvinylsulfonic acid, styrenesulfonic acid and vinylsulfonic acid;phosphonic acid monomers such as vinylphosphoric acid, etc.; or salts ofmonomers thereof, followed, as required, by a partial neutralizationwith an alkali.

As the other monomers copolymerizable therewith, though not limitedthereto only, there can be exemplified styrene, vinyltoluene,vinylxylene, α-methylstyrene, vinylnaphthalene, α-halogenated styrenes,acrylonitrile, acrolein, methyl vinyl ketone and vinylbiphenyl.

Instead of using the above anionic monomers, it is also allowable toobtain the anionic polymer (a2) by polymerizing an ester of the aboveanionic monomer or a monomer having a functional group capable ofintroducing the anionic functional monomer, such as styrene,vinyltoluene, vinylxylene, α-methylstyrene, vinylnaphthalene orα-halogenated styrenes followed by a treatment such as hydrolysis,sulfonation, chlorosulfonation or phosphoniation.

In the invention, a preferred example of the anionic polymer (a2) is apoly(meth)acrylic acid and a partly neutralized product thereof (e.g.,the one which is partly an Na salt).

The polymerization for forming the anionic polymer (a2) is, usually,carried out based on the radical polymerization by heating while using apolymerization initiator.

As the polymerization initiator, though there is no particularlimitation, there can be represented peroxides such as octanoylperoxide, lauroyl peroxide, t-butylperoxy-2-ethyl hexanoate, benzoylperoxide, t-butyl peroxyisobutylate, t-butyl peroxylaurate, t-hexylperoxybenzoate and di-t-butyl peroxide. Usually, the polymerizationinitiator is used in an amount of about 0.1 to about 20 parts by massand, specifically, about 0.5 to 10 parts by mass per 100 parts by massof the above-mentioned anionic monomer (or the monomer capable ofintroducing anionic groups).

The anionic polymer (a2) is obtained through the polymerization asdescribed above. However, if there is used the monomer capable ofintroducing the anionic functional groups, the treatment may beconducted for introducing the anionic groups, such as hydrolysis,sulfonation, chlorosulfonation or phosphoniation after thepolymerization has been finished.

<Hygroscopic Agent (b)>

The coating composition of the invention uses a granular crosslinkedproduct of a monovalent metal salt of a poly(meth)acrylic acid as thehygroscopic agent (b) that is to be dispersed in the matrix of the ionicpolymer (a).

The granular crosslinked product attains a humidity lower than thehumidity attained by the ionic polymer (a) (cationic polymer (a1) oranionic polymer (a2)) that forms the matrix, i.e., attains a humiditywhich is not 6% or lower under an environmental condition of a humidityof 80% RH and a temperature of 30° C. and thus has a very highhygroscopic property. That is, the coating formed by using the coatingcomposition of the invention contains dispersed therein a hygroscopicagent having a higher hygroscopic property than that of the matrix.Therefore, the moisture absorbed by the hygroscopic matrix is readilytrapped by the hygroscopic component, and water that is absorbed iseffectively confined in the matrix.

As a result, in the invention, water trapped in the coating iseffectively suppressed from being released; i.e., the coating not onlyexhibits its excellent hygroscopic property but is also effectivelysuppressed from swelling (suppressed from undergoing a dimensionalchange) despite of having absorbed water therein.

The crosslinked particles of the monovalent metal salt of thepoly(meth)acrylic acid are fine spherical particles obtained bypolymerizing and curing a (meth)acrylic monomer containing atrifunctional or more highly functional (meth) acrylate by thesuspension polymerization or the emulsion polymerization. Thecrosslinked particles have a mean primary particle diameter D₅₀ in arange of 1.00 nm or less and, specifically, 80 nm or less calculated asvolume as measured by, for example, the laser diffraction lightscattering method. The crosslinked particles can be homogeneously andfinely dispersed in the ionic polymer (a) that forms the matrix, do notimpair the transparency of the ionic polymer (a), have large specificsurface areas and, therefore, have a very high hygroscopic capabilityand hence exhibit excellent hygroscopic property as described above.

In the crosslinked particles of the monovalent metal salt of thepoly(meth)acrylic acid, the metal salt is, usually, an Na salt or a Ksalt. For instance, the crosslinked sodium polyacrylate fine particles(mean particle diameter of about 70 nm) in the form of a colloidaldispersion solution (pH=10.4) have been placed in the market by ToyoboCo., Ltd. in the trade name of TAFTIC HU-820E. It is also desired to usecrosslinked potassium polyacrylate fine particles of which is 80% ormore of the carboxyl groups have been neutralized with the potassiumsalt.

In the invention, it is very important that the hygroscopic agent (b)(crosslinked particles of the monovalent metal salt of the poly(meth)acrylic acid) is used in an amount of 75 to 700 parts by mass and,specifically, 100 to 600 parts by mass per 100 parts by mass of theionic polymer (a). That is, by using the hygroscopic agent (b) in theabove-mentioned amount, it is made possible to form the coating havingexcellent transparency and a smooth surface of a surface roughness Ra(maximum roughness) of 0.1 μm or more and, specifically, 0.08 μm ormore.

If, for example, the amount of the hygroscopic agent (b) is smaller thanthe above range, transparency of the coating is impaired; i.e., thecoating becomes white and, besides, its smoothness is impaired.Probably, if the amount of the hygroscopic agent (b) is small, it isconsidered that the crosslinked particles of the monovalent metal saltof the poly (meth) acrylic acid are distributed in a concentrated manneror are aggregated around the ionic groups of the ionic polymer. As aresult, the surface of the coating becomes rugged to a large extent,loses smoothness and, at the same time, causes light to be irregularlyreflected or scattered to a large degree also causing the transparencyto be impaired.

If the hygroscopic agent (b) is added in an amount larger than the aboverange, on the other hand, it is probable that applicability of thecoating composition tends to be impaired.

Namely, upon setting the amount of the hygroscopic agent (b) to liewithin the above range, fine particles are distributed in the coating ina state of being regularly arranged. As a result, excellent transparencyand surface smoothness can be secured.

<Solvent>

There is no particular limitation on the solvent used for the coatingcomposition of the present invention provided it can be volatilized andremoved by heating at a relatively low temperature. There can be used,for example, alcoholic solvents such as methanol, ethanol, propylalcohol and butanol; ketone solvents such as acetone and methyl ethylketone; mixed solvents of the above solvents with water; water; andaromatic hydrocarbon solvents such as benzene, toluene and xylene.Specifically, if the coating composition is to be blended with acrosslinking agent that will be described later, it is desired to usewater or a mixed solvent that contains water in order to accelerate thehydrolysis of a silane compound that has an alkoxysilyl group in thecrosslinking agent.

Here, the solvent is used in such an amount that the coating compositionacquires a viscosity suited for being applied.

<Other Blending Agents>

The coating composition of the present invention can be blended with acrosslinking agent and an adhesion improving agent depending on the kindof the ionic polymer (a) that is used as the matrix component.

The crosslinking agent is used for introducing the crosslinked structureinto the matrix in the coating. By using the crosslinking agent, it isallowed to maintain the mechanical strength without lowering thehygroscopic capability and, at the same time, to further improve thedimensional stability. That is, with the crosslinked structure beingintroduced into the hygroscopic matrix formed by using the ionic polymer(a), if water is absorbed by the matrix, molecules of the ionic polymer(matrix) are constrained by each other due to the crosslinking, and anincreased function is exhibited to suppress a change in the volumecaused by swelling (absorption of water).

If, for example, the cationic polymer (a1) is used as the ionic polymer(a) that forms the matrix, then there can be used, as the crosslinkingagent, a compound that has a crosslinking functional group (e.g., epoxygroup) capable of reacting with the cationic group possessed by thecationic polymer (a1) and a functional group (e.g., alkoxysilyl group)capable of forming a siloxane structure in the crosslinked structurethrough the hydrolysis and the dehydration-condensation. Specifically,there can be used a silane compound represented by the following formula(1):

X—SiR¹ _(n)(OR²)_(3-n)  (1)

-   -   wherein, X is an organic group having an epoxy group at the        terminal thereof, R¹ and R² are, respectively, methyl groups,        ethyl groups or isopropyl groups, and n is 0, 1 or 2.

The silane compound of the formula (1) has an epoxy group and analkoxysilyl group as functional groups, and the epoxy group undergoesthe addition reaction with a functional group (e.g., NH₂ group) of thecationic polymer (a1). On the other hand, the alkoxysilyl group forms asilanol group (SiOH group) through the hydrolysis thereof, forms thesiloxane structure through the condensation reaction thereof and,finally, forms the crosslinked structure among the cationic polymerchains. Therefore, the matrix formed by the cationic polymer (a1) has,introduced therein, the crosslinked structure having the siloxanestructure. On the other hand, if, for example, the base material onwhich the coating composition is applied is an inorganic material suchas glass or the like and has, on the surface thereof, an MOH group (M:metal element) such as SiOH group (silanol group), the silanol groupformed by the hydrolysis of the alkoxysilyl group undergoes thedehydration and condensation with this group and strongly bonds thereto.As a result, the coating adheres more closely to the base material.

Besides, in this case, the ionic polymer is the cationic polymer (a1).Therefore, the coating composition becomes alkaline and accelerates theaddition reaction of the cationic group with the epoxy group, and thedehydration and condensation between the silanol groups or of thecationic group with the MOH group on the surface of the base material.

By using the compound of the above formula (1) as the crosslinkingagent, therefore, it is made possible to introduce the crosslinkedstructure into the matrix and, depending on the kind of the basematerial on which the coating composition is applied, to improve closeadhesion between the coating and the base material without using anyparticular adhesive.

As the organic group X having the epoxy group in the above formula (1),there can be representatively used a γ-glycidoxyalkyl group. Forinstance, a γ-glycidoxypropyltrimethoxysilane or aγ-glycidoxypropylmethyldimethoxysilane is preferably used as thecrosslinking agent.

There can be, further, favorably used a crosslinking agent in which theepoxy group in the above formula (1) is an alicyclic epoxy group likeepoxycyclohexyl group. For instance, if there is used, as the crosslinking agent, a compound that has an alicyclic epoxy group likeβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, an alicyclic structure isintroduced together with the siloxane structure into the crosslinkedstructure of the matrix. Introduction of the alicyclic structure makesit possible to more effectively exhibit the function of the matrix whichis to form a spatial mesh structure adapted for adsorbing the moisture.

In the present invention, further, it is also allowable to use, as thecrosslinking agent, a compound that has a plurality of epoxy groups andalicyclic groups, e.g., a diglycidyl ester represented by the followingformula (2):

G-O(C═O)-A-(C═O)O-G  (2)

-   -   wherein, G is a glycidyl group and A is a divalent hydrocarbon        group having an aliphatic ring, such as cycloalkylene group.

A representative example of the diglycidyl ester is expressed by thefollowing formula (2-1).

That is, use of the diglycidyl ester of the formula (2) as thecrosslinking agent is effective in introducing the alicyclic structureinto the crosslinked structure and in forming the spatial mesh structurein the matrix that is adapted for absorbing the moisture.

In the invention, the amount of the above-mentioned crosslinking agentthat is used when the cationic polymer (a1) is used, is, desirably, 5 to60 parts by mass and, specifically, 15 to 50 parts by mass per 100 partsby mass of the cationic polymer (a1). Here, it is desired that at least70% or more by weight and, preferably, 80% or more by weight of thecrosslinking agent is the silane compound of the above formula (1).

If the crosslinking agent is used in too large amounts, the coatingcomposition becomes mechanically brittle and less easy to handle. If thecoating material is prepared, therefore, the viscosity increases soquickly that an effective pot life cannot be guaranteed. By using thecrosslinking agent in too small amounts, on the other hand, it maybecome difficult to guarantee the durability (e.g., mechanical strength)if the coating is exposed to severe environmental conditions (e.g.,highly humid conditions). Moreover, if the silane compound of the aboveformula (1) is used in too small amounts, the function may not be fullyexhibited for improving the adhesiveness of the coating to the basematerial.

If the anionic polymer (a2) is used as the ionic polymer (a), then therecan be used, as the crosslinking agent, a compound having two or morecrosslinking functional groups (e.g., epoxy groups) capable of reactingwith the anionic groups possessed by the anionic polymer (a2).Specifically, it is desired to use the diglycidyl ester represented bythe above formula (2), i.e.,

G-O(C═O)-A-(C═O)O-G  (2)

-   -   wherein, G is a glycidyl group, and A is a divalent hydrocarbon        group having an aliphatic ring, such as cycloalkylene group.

Namely, the diglycidyl ester is the same as the one that was used forintroducing the alicyclic structure into the crosslinked structure ofwhen the cationic polymer (a1) was used. By using the diglycidyl ester,two epoxy groups react with the anionic groups in the anionic polymer(a2), and the crosslinked structure is formed in the matrix, thecrosslinked structure having the alicyclic structure formed by thedivalent group A.

Due to the crosslinked structure that includes the alicyclic structure,molecules of the anionic polymer (a2) are constrained, and the swellingis suppressed. Specifically, from the standpoint of forming the spatialmesh structure adapted to absorbing the moisture, it is desired that thealiphatic ring included in the divalent organic group A is thecyclohexane ring. More desirably, the diglycidyl ester has two estergroups formed at positions neighboring to each other on the cyclohexanering. The diglycidyl ester of this structure is represented by theabove-mentioned formula (2-1).

Into the hygroscopic matrix formed by using the anionic polymer (a2), inparticular, there is introduced the crosslinked structure by using theabove-mentioned crosslinking agent in order to improve the dimensionalstability as a result of suppressing the swelling and to, further,improve the hygroscopic property.

Namely, in the case of the anionic polymer (a2), water is trappedrelying on the hydrogen bond only unlike the case of the cationicpolymer (a1). By forming the hydrophobic portions like the alicyclicstructure in the mesh structure, therefore, it is allowed to improve thehygroscopic effect at the hydrophilic portions.

In the invention, the amount of the above-mentioned crosslinking agentthat is used when the anionic polymer (a2) is used, is, desirably, 1 to50 parts by mass and, specifically, 10 to 40 parts by mass per 100 partsby mass of the anionic polymer (a2). If the crosslinking agent is usedin too large amounts, the coating may become brittle. Besides, if thecoating composition is prepared, the viscosity increases so quickly thatan effective pot life cannot be guaranteed. By using the crosslinkingagent in too small amounts, on the other hand, it may become difficultto guarantee the durability (e.g., mechanical strength) if the coatingis exposed to severe environmental conditions (e.g., highly humidconditions).

In the invention, further, when the anionic polymer (a2) is used as theionic polymer (a), use of the adhesion improving agent is particularlyeffective in forming the coating on the inorganic base material thatcomprises an inorganic material such as glass or metal.

That is, the adhesion improving agent has functional groups that reactwith the surface of the inorganic base material and with the anionicpolymer (a2), i.e., has an epoxy group and an alkoxysilyl group. As theadhesion improving agent, for example, there is preferably used thesilane compound represented by the above-mentioned formula (1):

X—SiR¹ _(n)(OR²)_(3-n)  (1)

-   -   wherein, X is an organic group having an epoxy group at the        terminal thereof, R¹ and R² are, respectively, methyl groups,        ethyl groups or isopropyl groups, and n is 0, 1 or 2.

The above silane compound is the same compound as the one that is usedas the crosslinking agent when the cationic polymer (a1) is used.

In the silane compound, the silanol group (SiOH group) formed by thehydrolysis of the alkoxysilyl group undergoes the dehydration andcondensation with the MOH (M is a metal element such as Si) distributedin the surface of the inorganic base material. Therefore, the siloxanestructure is introduced into the matrix, and the adhesive agent (silanecompound) closely bonds to the surface of the inorganic base materialdue to the siloxane bond. Besides, the epoxy group in the silanecompound undergoes the reaction (esterification) with the acid group(e.g., COOH) or a salt thereof (e.g., COONa) possessed by the anionicpolymer (a2), and bonds thereto. Therefore, the adhesion improving agentalso bonds to the matrix in the coating.

Thus the adhesion improving agent improves the degree of adhesion andthe strength of adhesion between the coating and the inorganic basematerial. As a result, the coating is effectively prevented frompeeling, and maintains its properties over extended periods of time.

Among the silane compounds of the above formula (1), it is desired touse those having a plurality of alkoxysilyl groups (n is 0 or 1 in theformula (1)), such as γ-glycidoxypropyltrimethhoxysilane andγ-glycidoxypropylmethyldimethoxysilane. Further, the most desiredadhesion improving agents are those in which the epoxy group is analicyclic epoxy group like epoxycyclohexyl group, such asβ-(3,4-epoxycyclohexyl) ethyltrimethoxysilane and the like.

In the invention, it is desired that the adhesion improving agent isused in an amount of 0.1 to 10 parts by mass and, specifically, 1 to 8parts by mass per 100 parts by mass of the anionic polymer (a2) suchthat the properties thereof are exhibited to a sufficient degree withoutimpairing the hygroscopic properties mentioned above.

The coating composition of the invention can be, further, blended with anon-ionic polymer in a suitable amount in order to adjust the viscosityof the coating composition or to adjust the water-absorbing ratio of theformed hygroscopic matrix to lie in a suitable range.

As the non-ionic polymer, there can be exemplified saturated aliphatichydrocarbon polymers such as polyvinyl alcohol, ethylene-propylenecopolymer and polybutylene; styrene polymers such as styrene-butadienecopolymer, etc.; polyvinyl chloride; as well as those of the abovepolymers that are, further, copolymerized with various kinds ofcomonomers (e.g., styrene monomers such as vinyl toluene, vinyl xylene,chlorostyrene, chloromethylstyrene, α-methylstyrene, α-halogenatedstyrene, and α, β, β′-trihalogenated styrene; monoolefins such asethylene and butylene; and conjugated diolefins such as butadiene andisoprene).

<Forming the Coating and its Use>

The above coating composition is applied onto the surfaces of variousbase materials such as of plastic material, glass and metal, and isheated in a heating oven to remove the solvent, and a coating thereof isformed. The temperature of heating is, usually, about 80 to about 160°C. and the time of heating is, usually, from about several seconds toabout several minutes though it may vary depending upon the coatingcomposition, capability of the heating oven and the thickness of thecoating.

The solvent is removed by heating and coating is formed. If the coatingcomposition is blended with a crosslinking agent, a crosslinkedstructure is introduced by heating into the matrix formed by the ionicpolymer (a). Further, if the coating composition is applied onto thebase material (e.g., glass base material) having MOH (M: metal elementsuch as Si) in the surface thereof, the crosslinking agent reacts withthe MOH, and close adhesion is improved between the coating and the basematerial.

The thickness of the coating is not specifically limited and may besuitably set depending on the use and the required properties.

As described above already, the coating has excellent hygroscopicproperty, dimensional stability, transparency and surface smoothness. Byutilizing these properties, therefore, the coating is used for a varietyof applications.

For a variety of devices such as organic EL devices and solar cells thatrequire transparency, for example, the coating composition can be usedas a water-barrier agent by utilizing the transparency, dimensionalstability and hygroscopic property of the coating thereof.

The coating composition (water-barrier agent) is applied onto atransparent base plate such as of a transparent plastic material or aglass to form a coating thereof. That is, the coating works as a watershut-off film while absorbing very small amounts of water in the device.Therefore, electronic circuitry formed on the transparent base plate isprevented from being deteriorated with water.

If the transparent plastic base plate is to be coated with the coatingcomposition, it is desired that a silicon oxide has been deposited inadvance on the surface of the transparent plastic base plate by the CVDmethod to further improve the water shut-off property.

The coating composition can be, further, used as a defogging agent byutilizing the transparency, hygroscopic property, dimensional stabilityand surface smoothness of the coating that is formed. That is, thecoating composition is applied on the surface of a mirror, a windowpane,a transparent packing material (e.g., polyethylene terephthalate bottle)or the like to form a coating thereof which then serves as a defoggingfilm. Namely, water droplets may happen to adhere to the smooth surfaceof the transparent coating. The water droplets, in this case, spread onthe surface to form a thin liquid film thereof due to a high degree ofhygroscopic property of the coating. This suppresses irregularreflection or scattering of light caused by the adhesion of waterdroplets. Namely, this effectively prevents the fogging caused by theirregular reflection or the scattering of light and makes it possible toeffectively maintain optical properties (reflection and transmission oflight) of the base material.

EXAMPLES

Excellent properties of the coating formed by using the coatingcomposition of the invention will now be described by way ofExperimental Examples.

<Evaluating the Attained Humidity>

The coating was dried at 140° C. for one hour. 0.5 Grams of the materialto be measured and a wireless thermometer/hygrometer (Hygroclone,manufactured by KN Laboratories, Inc.) were put into a cup of awater-impermeable steel-foiled laminate having a volume of 85 cm³. Themouth of the container was heat-sealed with a lid of an aluminumfoil-laminated film. After left to stand at 30° C.80% RH for one day,the relative humidity in the container was regarded as the attainedhumidity.

<Measuring the Saturated Hygroscopic Amount>

The saturated hygroscopic amount in the hygroscopic layer was foundaccording to the following procedure.

The weight (X) of the glass base plate was measured.

A hygroscopic film was formed on the glass base plate, dried at 140° C.for one hour, and was measured for its weight (Y).

Next, the sample was left to stand in an air-conditioned vessel in whichthe atmosphere was adjusted to be 30° C. 80% RH for 24 hours, and wasmeasured for its weight (Z) after it has absorbed moisture.

From the above measured results, the saturated hygroscopic amount of thehygroscopic film was calculated according to the following formula,

(Z—Y)/(Y—X)

and was evaluated on the following basis.

-   -   ⊚: The saturated hygroscopic amount was 0.7 g/g or more.    -   ◯: The saturated hygroscopic amount was 0.6 or more but was not        more than 0.7 g/g.    -   X: The saturated hygroscopic amount was not more than 0.6 g/g.

<Measuring the Contact Angle of Water>

A 3-μL of water droplet was caused to drop on the surface of thehygroscopic film formed on the glass base plate. After one minute haspassed, the water droplet was measured for its angle of contact and wasevaluated on the following basis.

-   -   ◯: The contact angle of water is 40 degrees or less.    -   X: The contact angle of water is more than 40 degrees.

<Measuring the Hazes>

By using an SM color computer (SM-4, manufactured by Suga TestInstruments Co., Ltd.), the hygroscopic film was measured for its hazein compliance with the JIS-K7361-1, and was evaluated on the followingbasis.

-   -   ◯: The haze is 5% or less.    -   X: The haze is more than 5%.

<Measuring the Maximum Surface Roughness Ra (JIS B-0601-1994)>

A maximum surface roughness Ra of the surface of the hygroscopic filmformed on the glass base plate was measured by using an interatomicforce microscope (NanoScope III, manufactured by Digital InstrumentsCo.), and was evaluated on the following basis.

-   -   ◯: Maximum surface roughness Ra is 0.1 μm or less.    -   X: Maximum surface roughness Ra is more than 0.1 μm.

<Evaluating the Defogging Capability>

The surface of the hygroscopic film formed on the glass base plate wasexposed over a warm water bath heated at 40° C., measured for itsdefogging time (in minutes) until it was fogged or distorted due towater film, and was evaluated on the following basis.

-   -   ◯: Was not fogged for one minute or more.    -   X: Fogged in less than one minute.

Example 1

The following compounds were provided as the cationic polymer and thehygroscopic agent.

Cationic Polymer;

-   -   PAA-15C (aqueous solution) containing 15% by mass of a solid        component, manufactured by Nittobo Medical Co., Ltd.

Hygroscopic Agent;

-   -   Crosslinked product of Na polyacrylate.    -   TAFTIC HU-820E (aqueous dispersion) containing 13% by mass of a        solid component, manufactured by Toyobo Co., Ltd.

A polymer solution was obtained by diluting the above cationic polymer(polyallylamine) with water such that the solid component thereof was 5%by weight.

On the other hand, a solution of the crosslinking agent was prepared bydissolving a γ-glycidoxypropyltrimethoxysilane, as the crosslinkingagent, in water such that the amount thereof was 5% by weight.

Next, the polymer solution and the solution of the crosslinking agentwere mixed together such that the amount of theγ-glycidoxypropyltrimethoxysilane was 15 parts by weight per 100 partsby weight of the polyallylamine. To the mixed solution was, further,added the above hygroscopic agent (crosslinked product of Napolyacrylate) in an amount of 410 parts by weight with respect to thecationic polymer, and to which was, further, added water such that theamount of the solid component was 5%. The mixture was stirred well toobtain a coating solution.

By using a bar coater, the above coating solution was applied onto aclean glass that has been polished and washed. The film after appliedwas heat-treated in a box-type electric oven under the conditions of apeak temperature of 120° C. and a peak temperature-holding time of 10seconds. There was formed a coating of a thickness of 4 Mm.

Example 2

By using an ion-exchange resin (Amberlite 200CT produced by OrganoCorporation), the Na salt-type carboxyl groups of the crosslinkedproduct (HU-820E) of the Na polyacrylate were converted into the H-typecarboxyl groups. Thereafter, by using a 1 N aqueous solution of thepotassium hydroxide, there was obtained a crosslinked product (aqueousdispersion) of the K polyacrylate having K salt-type carboxyl groups.

Properties of the crosslinked product were as described below.

Crosslinked product (aqueous dispersion) of the K polyacrylate;

-   -   Solid component: 10% by mass    -   Mean particle diameter D₅₀: 70 nm    -   Neutralization ratio: 80%

A coating was formed in the same manner as in Example 1 but using thecrosslinked product of the above K polyacrylate as the hydroscopicagent.

Example 3

A crosslinked product (aqueous dispersion) of the K polyacrylate wasobtained in the same manner as in Example 2 but using a 1 N aqueoussolution of the lithium hydroxide instead of using the 1 N aqueoussolution of the potassium hydroxide.

By using the crosslinked product, a coating was formed in the samemanner as in Example 2.

Example 4

A crosslinked product (aqueous dispersion) of the cesium polyacrylatewas obtained in the same manner as in Example 2 but using a 1 N aqueoussolution of the cesium hydroxide instead of using the 1 N aqueoussolution of the potassium hydroxide. By using the crosslinked product, acoating was formed in the same manner as in Example 2.

Example 5

A coating was formed in the same manner as in Example 1 but adding thehydroscopic agent in an amount of 100 parts by weight relative to thepolyallylamine.

Example 6

A coating was formed in the same manner as in Example 1 but adding thehydroscopic agent in an amount of 700 parts by weight relative to thepolyallylamine.

Example 7

A coating was formed in the same manner as in Example 1 but so mixingthe polymer solution and the crosslinking agent solution that the amountof the γ-glycidoxypropyltrimethoxysilane which is the crosslinking agentwas 7 parts by weight relative to the polyallylamine and, further,adding the hygroscopic agent in an amount of 380 parts by weightrelative to the polyallylamine.

Example 8

A coating was formed in the same manner as in Example 1 but so mixingthe polymer solution and the crosslinking agent solution that the amountof the γ-glycidoxypropyltrimethoxysilane which is the crosslinking agentwas 50 parts by weight relative to the polyallylamine and, further,adding the hygroscopic agent in an amount of 530 parts by weightrelative to the polyallylamine.

Example 9

A coating was formed in the same manner as in Example 1 but using aβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane as the crosslinking agent.

Example 10

A coating was formed in the same manner as in Example 1 but so mixingthe polymer solution and the crosslinking agent solution that the amountof the γ-glycidoxypropyltrimethoxysilane which is the crosslinking agentwas 16 parts by weight relative to the polyallylamine and, further,adding, as the crosslinking agent, a diglycidyl1,2-cyclohexanedicarboxylate in an amount of 4 parts by weight relativeto the polyallylamine.

Example 11

A coating was formed in the same manner as in Example 1 but using, asthe solvent in the coating solution, a mixed solvent of water andacetone (at a weight ratio of 80/20) instead of using water only,adding, as the crosslinking agent, the diglycidyl1,2-cyclohexanedicarboxylate in an amount of 20 parts by weight per 100parts by weight of the polyallylamine, and, further, adding thehygroscopic agent in an amount of 170 parts by weight relative to thepolyallylamine.

Example 12

A coating was formed in the same manner as in Example 1 but using apolyethyleneimine (Polyethyleneimine 10000 manufactured by JunseiChemical Co., Ltd.) as the ionic polymer.

Example 13

A coating was formed in the same manner as in Example 1 but using, asthe ionic polymer, a polyacrylic acid (AC-10LP manufactured by NihonJunyaku Co.) that was partly neutralized by 80% with the sodiumhydroxide, using, as the solvent, a mixed solvent of water and acetone(at a weight ratio of 80/20), using, as the crosslinking agent, adiglycidyl 1,2-cyclohexanedicarboxylate in an amount of 15 parts byweight relative to the partly neutralized product of the polyacrylicacid, using, as the adhesive agent, aβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane in an amount of 3 parts byweight relative to the partly neutralized product of the polyacrylicacid, and adding the hygroscopic agent in an amount of 410 parts byweight relative to the partly neutralized product of the polyacrylicacid.

Example 14

A coating was formed in the same manner as in Example 13 but using thehygroscopic agent in an amount of 100 parts by weight relative to thepartly neutralized product of the polyacrylic acid.

Example 15

A coating was formed in the same manner as in Example 13 but using thehygroscopic agent in an amount of 700 parts by weight relative to thepartly neutralized product of the polyacrylic acid.

Example 16

A coating was formed in the same manner as in Example 13 but adding thediglycidyl 1,2-cyclohexanedicarboxylate that is the crosslinking agentin an amount of 1 part by weight relative to the partly neutralizedproduct of the polyacrylic acid and adding the hygroscopic agent in anamount of 365 parts by weight relative to the partly neutralized productof the polyacrylic acid.

Example 17

A coating was formed in the same manner as in Example 13 but adding thediglycidyl 1,2-cyclohexanedicarboxylate that is the crosslinking agentin an amount of 50 parts by weight relative to the partly neutralizedproduct of the polyacrylic acid and adding the hygroscopic agent in anamount of 540 parts by weight relative to the partly neutralized productof the polyacrylic acid.

Example 18

A coating was formed in the same manner as in Example 13 but adding theβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane that is the adhesive agentin an amount of 0.3 parts by weight relative to the partly neutralizedproduct of the polyacrylic acid and adding the hygroscopic agent in anamount of 420 parts by weight relative to the partly neutralized productof the polyacrylic acid.

Example 19

A coating was formed in the same manner as in Example 13 but adding theβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane that is the adhesive agentin an amount of 10 parts by weight relative to the partly neutralizedproduct of the polyacrylic acid and adding the hygroscopic agent in anamount of 460 parts by weight relative to the partly neutralized productof the polyacrylic acid.

Example 20

A coating was formed in the same manner as in Example 13 but partlyneutralizing the polyacrylic acid to a ratio of 50%, using an ethyleneglycol diglycidyl ether as the crosslinking agent, and conducting theheat treatment at a temperature of 160° C.

Comparative Example 1

A coating was formed in the same manner as in Example 1 but adding thehygroscopic agent in an amount of 30 parts by weight relative to thepolyallylamine.

Comparative Example 2

A coating was formed in the same manner as in Example 13 but adding thehygroscopic agent in an amount of 30 parts by weight relative to thepartly neutralized product of the polyacrylic acid.

Comparative Example 3

A coating was formed in the same manner as in Example 1 but using apolyvinyl alcohol (PVA103 manufactured by Kuraray Co., Ltd.) instead ofusing the ionic polymer.

<Tests for Evaluation>

The coatings formed in the above Examples and Comparative Examples weremeasured for their properties by the methods described above. Tables 1to 3 show the compositions of the coatings while Tables 4 to 6 show themeasured results.

The coatings of Comparative Examples 1 to 3 possessed so lowtransparencies that their defogging properties were not evaluated.

The following Tables use the following abbreviations.

γ-GLY-silane:

-   -   γ-glycidoxypropyltrimethylsilane

β-EPO-silane:

β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane 1,2-DCA-diglycidyl:

diglycidyl 1,2-cyclohexanedicarboxylate

ETGDGL-ether:

ethylene glycol diglycidyl ether

TABLE 1 *1 *2 *3 *4 *5 *6 *7 Ex. 1 polyallylamine — 7.1 HU-820E 0.0γ-GLY-silane — (100) (410) (15) Ex. 2 polyallylamine — 7.1 K salt type0.0 γ-GLY-silane — (100) (410) (15) Ex. 3 polyallylamine — 7.1 Li salttype 0.0 γ-GLY-silane — (100) (410) (15) Ex. 4 polyallylamine — 7.1 Casalt type 0.0 γ-GLY-silane — (100) (410) (15) Ex. 5 polyallylamine — 7.1HU-820E 0.0 γ-GLY-silane — (100)  (80) (15) Ex. 6 polyallylamine — 7.1HU-820E 0.0 γ-GLY-silane — (100) (700) (15) Ex. 7 polyallylamine — 7.1HU-820E 0.0 γ-GLY-silane — (100) (380) (7) Ex. 8 polyallylamine — 7.1HU-820E 0.0 γ-GLY-silane — (100) (530) (50) Ex. 9 polyallylamine — 7.1HU-820E 0.0 β-EPO-silane — (100) (430) (20) Ex. 10 polyallylamine — 7.1HU-820E 0.0 γ-GLY-silane (16) — (100) (430) 1,2-CYDC-diglycidyl (4) *1Ionic polymer (amount), *2 Neutralization ratio (%), *3 Humidityattained by ionic polymer (% RH), *4 Hygroscopic agent (amount), *5Humidity attained by hygroscopic agent (% RH), *6 Crosslinking agent(amount), *7 Adhesive agent (amount)

TABLE 2 *1 *2 *3 *4 *5 *6 *7 Ex. 11 polyallylamine — 7.1 HU-820E 0.01,2-CYDC-diglycidyl — (100) (170) (20) Ex. 12 polyethyleneimine — 7.3HU-820E 0.0 γ-GLY-silane — (100) (410) (15) Ex. 13 polyacrylicacid 807.9 HU-820E 0.0 1,2-CYDC-diglycidyl β-EPO-silane (100) (410) (15)   (3)Ex. 14 polyacrylicacid 80 7.9 HU-820E 0.0 1,2-CYDC-diglycidylβ-EPO-silane (100)  (80) (15)   (3) Ex. 15 polyacrylicacid 80 7.9HU-820E 0.0 1,2-CYDC-diglycidyl β-EPO-silane (100) (700) (15)   (3) Ex.16 polyacrylicacid 80 7.9 HU-820E 0.0 1,2-CYDC-diglycidyl β-EPO-silane(100) (365)  (1)   (3) Ex. 17 polyacrylicacid 80 7.9 HU-820E 0.01,2-CYDC-diglycidyl β-EPO-silane (100) (540) (50)   (3) Ex. 18polyacrylicacid 80 7.9 HU-820E 0.0 1,2-CYDC-diglycidyl β-EPO-silane(100) (420) (20) (0.3) Ex. 19 polyacrylicacid 80 7.9 HU-820E 0.01,2-CYDC-diglycidyl β-EPO-silane (100) (460) (20)  (10) Ex. 20polyacrylicacid 50 18.0 HU-820E 0.0 ETGDGL-ether β-EPO-silane (100)(430) (20)   (3) *1 Ionic polymer (amount), *2 Neutralization ratio (%),*3 Humidity attained by ionic polymer (% RH), *4 Hygroscopic agent(amount), *5 Humidity attained by hygroscopic agent (% RH), *6Crosslinking agent (amount), *7 Adhesive agent (amount)

TABLE 3 *1 *2 *3 *4 *5 *6 *7 Comp. polyallylamine — 7.1 HU-820E 0.0γ-GLY-silane — Ex. 1 (100)  (30) (15) Comp. polyacrylicacid 80 7.9HU-820E 0.0 1,2-CYDC-diglycidyl β-EPO-silane Ex. 2 (100)  (30) (15) (3)Comp. polyvinylalcohol — 68.0 HU-820E 0.0 γ-GLY-silane — Ex. 3 (100)(410) (15) *1 Ionic polymer (amount), *2 Neutralization ratio (%), *3Humidity attained by ionic polymer (% RH), *4 Hygroscopic agent(amount), *5 Humidity attained by hygroscopic agent (% RH), *6Crosslinking agent (amount), *7 Adhesive agent (amount)

TABLE 4 Saturated Water hygroscopic contact Surface amount angle Hazeroughness Defogging (g/g) (deg.) (%) (μm) property Ex. 1 ⊚ ◯ ◯ ◯ ◯(0.78) (33) (2.5) (0.04) Ex. 2 ⊚ ◯ ◯ ◯ ◯ (0.73) (19) (2.7) (0.04) Ex. 3⊚ ◯ ◯ ◯ ◯ (0.81) (30) (2.3) (0.05) Ex. 4 ⊚ ◯ ◯ ◯ ◯ (0.60) (35) (2.3)(0.04) Ex. 5 ⊚ ◯ ◯ ◯ ◯ (0.74) (39) (4.1) (0.1)  Ex. 6 ⊚ ◯ ◯ ◯ ◯ (0.73)(31) (2.2) (0.04) Ex. 7 ⊚ ◯ ◯ ◯ ◯ (0.71) (35) (2.4) (0.04) Ex. 8 ⊚ ◯ ◯ ◯◯ (0.74) (37) (2.7) (0.04) Ex. 9 ⊚ ◯ ◯ ◯ ◯ (0.75) (33) (2.7) (0.04) Ex.10 ⊚ ◯ ◯ ◯ ◯ (0.73) (34) (2.1) (0.04)

TABLE 5 Saturated Water hygroscopic contact Surface amount angle Hazeroughness Defogging (g/g) (deg.) (%) (μm) property Ex. 11 ⊚ ◯ ◯ ◯ ◯(0.78) (38) (2.5) (0.07) Ex. 12 ⊚ ◯ ◯ ◯ ◯ (0.71) (36) (2.4) (0.04) Ex.13 ⊚ ◯ ◯ ◯ ◯ (0.79) (33) (2.2) (0.05) Ex. 14 ⊚ ◯ ◯ ◯ ◯ (0.78) (36) (4.8)(0.09) Ex. 15 ⊚ ◯ ◯ ◯ ◯ (0.79) (37) (2.1) (0.04) Ex. 16 ⊚ ◯ ◯ ◯ ◯ (0.76)(39) (2.5) (0.05) Ex. 17 ⊚ ◯ ◯ ◯ ◯ (0.74) (36) (2.0) (0.06) Ex. 18 ⊚ ◯ ◯◯ ◯ (0.73) (40) (2.5) (0.06) Ex. 19 ⊚ ◯ ◯ ◯ ◯ (0.78) (39) (2.0) (0.05)Ex. 20 ◯ ◯ ◯ ◯ ◯ (0.60) (33) (2.0) (0.1) 

TABLE 6 Saturated Water hygroscopic contact Surface amount angle Hazeroughness Defogging (g/g) (deg.) (%) (μm) property Comp. ◯ ◯ X X — Ex. 1(0.63) (39) (29.8) (0.28) Comp. ◯ ◯ X X — Ex. 2 (0.66) (40) (85.1)(0.45) Comp. ◯ ◯ X X — Ex. 3 (0.61) (39) (43.1) (0.36)

1. A coating composition comprising an ionic polymer (a), a hygroscopicagent (b) and a solvent, the hygroscopic agent (b) being a granularcrosslinked product of a monovalent metal salt of a poly(meth)acrylicacid and being contained in an amount of 75 to 700 parts by mass per 100parts by mass of the ionic polymer (a).
 2. The coating compositionaccording to claim 1, wherein the coating composition is used forforming a defogging film.
 3. The coating composition according to claim1, wherein the coating composition is used for forming a water shut-offfilm.
 4. The coating composition according to claim 1, wherein the ionicpolymer (a) is a cationic polymer (a1).
 5. The coating compositionaccording to claim 1, wherein the ionic polymer (a) is an anionicpolymer (a2).
 6. A coating formed on a surface of a base material, acoating comprising a matrix of an ionic polymer (a) and a hygroscopicagent (b) dispersed in the matrix, and the hygroscopic agent (b) being agranular crosslinked product of a monovalent metal salt of apoly(meth)acrylic acid and being contained in an amount of 75 to 700parts by mass per 100 parts by mass of the ionic polymer (a).
 7. Thecoating according to claim 6, wherein the coating has a haze of 5% orless and a maximum surface roughness Ra (JIS B-0601-1994) of 0.1 μm orless.
 8. The coating according to claim 6, wherein the coating is usedas a water shut-off film.
 9. The coating according to claim 6, whereinthe coating is used as a defogging film.
 10. A method of forming a watershut-off film or a defogging film on a surface of a base material byapplying the coating composition described in claim 1 on the surface ofthe base material followed by heating to remove a solvent.